NEMATODE-RESISTANT TRANSGENIC PLANTS

Abstract: Nematode-resistant transgenic plants are disclosed. The plants comprise plant cells containing a DNA construct comprising a transcription cassette, which construct comprises, in the 5' to 3' direction, a promoter operable in the plant cells, and a DNA comprising at least a portion of a DNA sequence encoding a nematode-inducible transmembrane pore protein in either the sense or antisense orientation. Intermediates for producing the same along with methods of making and using the same are also disclosed. In an alternate embodiment of the invention, the sense or antisense DNA is replaced with a DNA encoding an enzymatic RNA molecule directed against the mRNA transcript of a DNA sequence encoding a nematode-inducible transmembrane pore protein.

Description: NEMATODE-RESISTANTTRANSGENIC PLANTS This invention was made with government support under grant number DMB 88-11077 from the National Science Foundation. The Government may have certain rights to this invention. Field of the Invention This invention relates to methods of controlling plant-parasitic nematodes by application of recombinant DNA technology and the production of transgenic plants. Background ofthe Invention World-wide, plant-parasitic nematodes are among the most devastating pathogens of life sustaining crops. In 1984, nematodes accounted for more than fifty billion dollars (US) in economic losses. The United States' portion of this figure alone is almost six billion dollars. Genetic resistance to certain nematode species is available in some cultivars, but these are restricted in number, and the availability of cultivars with both desirable agronomic features and resistance is limited. In addition, traditional methods for plant breeding require 5-10 years to produce a viable cultivar, while the need for new nematode control tools is immediate and critical. The major means of nematode control has been the application of chemical nematicides. During 1982, in the United States alone over 100 million pounds of nematicide were applied to crops. Chemical nematicides are generally highly toxic compounds known to cause substantial environmental impact. In the past several years, issues such as ground water contamination, mammalian and avian toxicity, and residues in food have caused much tighter restrictions on the use of chemical nematicides. Unfortunately, in many situations there is no alternative available for growers who rely upon nematicides to protect their crop from root-knot and cyst nematodes. Accordingly, there is a continuing need for new ways to combat nematodes in plants. Summary ofthe Invention A first aspect of the present invention is a DNA construct comprising a transcription cassette. The construct comprises, in the 5' to 3' direction, (a) a promoter operable in a plant cell, (b) a DNA comprising at least 15 nucleotides of a DNA sequence encoding a nematode- inducible transmembrane pore protein in either the opposite orientation for expression (i.e., an antisense DNA) or the proper orientation for expression (i.e., a sense DNA), and (c) optionally, but preferably, a termination signal. The promoter may be one which is constitutively active in plant cells, selectively active in plant root tissue cells, or a nematode-responsive element such as the nematode-responsive element of the Tobacco RB7 (TobRB7) promoter. Such constructs may be carried by a plant transformation vector such as an Agrobacterium tumefaciens vector, which are in turn used to produce recombinant plants. A second aspect of the present invention is, accordingly, a nematode-resistant transgenic plant. The plant comprises cells containing a DNA construct comprising a transcription cassette as described above. In particular embodiments of the invention, DNA encoding a nematode-inducible transmembrane pore protein may be selected from the group consisting of: (a) isolated DNA having the sequence given herein as SEQ ID N0:1 (which DNA encodes the nematode-inducible transmembrane pore protein given herein as SEQ ID NO:2) or SEQ ID NO:6 (which is a genomic DNA encoding the nematode-inducible transmembrane pore protein given herein as SEQ ID NO:7, which is the same as SEQ ID NO:2) ; (b) isolated DNA which hybridizes to isolated DNA of (a) above and which encodes a nematode inducible transmembrane pore protein (which isolated DNA is preferably at least 50% homologous with an isolated DNA of (a) above; and which pore protein is preferably at least 60% homologous with a pore protein of (a) above) ; and (c) isolated DNA differing from the isolated DNAs of (a) and (b) above in nucleotide sequence due to the degeneracy of the genetic code, and which encode a nematode-inducible transmembrane pore protein. A specific example of such a DNA, in antisense configuration for carrying out the present invention, is given herein as SEQ ID NO:3. Additionally, in particular embodiments of the invention, DNA encoding a nematode-responsive element may be selected from the group consisting of: (i) isolated DNA having the sequence given herein as SEQ ID NO:5; and (ii) isolated DNA which hybridizes to isolated DNA of (i) above and which encodes a nematode responsive element (which is preferably at least 60% homologous to isolated DNA of (i) above; and which are preferably at least 10 or 15 nucleotides in length) (this definition is intended to include fragments of (i) above which retain activity as nematode-responsive elements) . The foregoing and other objects and aspects of this invention are explained in detail in the drawings herein and the specification set forth below. Brief Description of the Drawings Figure 1 illustrates a pair of DNA constructs comprising transcription cassettes, one in which the TobRB7 cDNA in sense configuration under the transcriptional control of a CaMV 35S promoter, and the other with a TobRB7 cDNA in antisense configuration under the transcriptional control of a CaMV 35S promoter. A nos 3' termination sequence and a neomycin phosphotransferase II (NPT-II) selectable marker for imparting kanamycin resistance is provided in both cases. The border regions of the Ti plasmid into which the cassette is inserted are indicated as "TiB". Figure 2 illustrates transcription cassettes much like those illustrated in Figure 1 above, except that the constitutively active CaMV35S promoter is replaced with either the element TobRB7 Δθ.6 which is selectively active in root tissue cells or the nematode-responsive element TobRB7 Δ0.3. Detailed Description of the Invention The present invention is employed to combat nematodes, particularly the root knot nematodes (Meloidogyne spp.) and the cyst nematodes (Globodera spp. and Heterodera spp.). These nematodes have similar life cycles. Root-knot nematodes are sedentary endoparasites with an extremely intimate and complex relationship to the host plant. The infective second stage juvenile (J2) is free in the soil. Upon location of a host root, the J2 penetrates the root intercellularly in the region just posterior to the root cap and migrates to the developing vascular cylinder. The nematode then orients itself parallel to the cylinder and injects glandular secretions into the plant cells surrounding its head, resulting in the initiation of nematode feeding cells. These 5-7 cells undergo rapid nuclear divisions, increase tremendously in size, and become filled with pores and cell wall invaginations. The feeding site cells, or "giant cells", function as super transfer cells to provide nourishment to the developing nematode. During this time, the nematode loses the ability to move and swells from the normal eel shaped J2 to a large, pear shaped adult female. As the nematode feeds on the giant cells, parthenogenic reproduction results in the the disposition of 300-1000 eggs. This entire process occurs over the span of 20-30 days, and root-knot nematodes may complete as many as 7 generations during a cropping season. The life cycle of the cyst nematode is essentially the same, except that its feeding site is referred to as a "syncytia", and it undergoes sexual reproduction. Nematode-inducible transmembrane pore proteins are pore proteins the expression of which is increased in cells upon infection of a plant containing the cells by a plant-parasitic nematode at a position adjacent those cells. Increased expression of such pore proteins is required by the nematode in establishing a feeding site capable of passing nutrients from the plant to the nematode. In general, and as explained in greater detail below, DNA encoding nematode-inducible transmembrane pore proteins include DNA which is 50% homologous or more with DNA having the sequence given herein as SEQ ID NO:l or SEQ ID NO:6. With respect to the protein, DNA encoding nematode-inducible transmembrane pore proteins encode a protein which, in amino acid content, is about 60% homologous or more, or preferably about 70% homologous or more, with the protein having the amino acid sequence given herein as SEQ ID NO:2. Determinations of homology are made with the two sequences (nucleic acid or amino acid) aligned for maximum matching. Gaps in either of the two sequences being matched are allowed in maximizing matching. Gaps lengths of 10 or less are preferred, gap lengths of 5 or less are more preferred, and gap lengths of 2 or less still more preferred. Differential hybridization procedures are available which allow for the isolation of cDNA clones whose mRNA levels are as low as about 0.05% of poly(A + )RNA. See M. Conkling et al., Plant Physiol . 93, 1203-1211 (1990) . In brief, cDNA libraries are screened using single-stranded cDNA probes of reverse transcribed mRNA from plant tissue (i.e., roots and leaves). For differential screening, a nitrocellulose or nylon membrane is soaked in 5xSSC, placed in a 96 well suction manifold, 150 μL of stationary overnight culture transferred from a master plate to each well, and vacuum applied until all liquid has passed through the filter. 150 μL of denaturing solution (0.5M NaOH, 1.5 M NaCl) is placed in each well using a multiple pipetter and allowed to sit about 3 minutes. Suction is applied as above and the filter removed and neutralized in 0.5 M Tris-HCl (pH 8.0), 1.5 M NaCl. It is then baked 2 hours in vacuo and incubated with the relevant probes. By using nylon membrane filters and keeping master plates stored at -70°C in 7% DMSO, filters may be screened multiple times with multiple probes and appropriate clones recovered after several years of storage. For example, to isolate genes whose expression is induced or enhanced by nematode infection, a cDNA library of mRNA isolated from nematode infected tobacco roots is constructed. The roots are staged such that mRNA is isolated at the time of giant cell initiation. The library is then screened by the procedures given above using single stranded cDNA probes of mRNA isolated from nematode-infected and control roots. Those cDNA clones exhibiting differential expression are then used as probes on tobacco genomic Southern blots (to confirm the cDNA corresponds to tobacco and not nematode transcripts) and Northern blots of root RNA from infected and control tissue (to confirm differential expression) . Those clones exhibiting differential expression are then used as probes to screen an existing tobacco genomic library. Essentially the same procedure is carried out with plants other than tobacco and nematodes (or other pathogens) other than root- knot nematodes. The procedure is useful for identifying promoters induced by cyst nematodes, in which case the roots are staged such that mRNA is isolated at the time of syncytia initiation. For example, a potato-cyst nematode (Globodera spp.) inducible promoter is isolated from potato plants (Solanum tuberosum) in accordance with the foregoing procedures. We have probed a wide variety of dicotyledonous and monocotyledonous plants at low stringency with TobRB7 probes and have found that most (if not all) plants contain a TobRB7 analog. We have already identified by low stringency hybridization such a root-specific cDNA analog from Arabidopsiε thaliana (AtRB7) (Yamamoto, Cheng, and Conkling 1990 Nucl . Acids Res. 18: 7449). Nematode-inducible transmembrane pore proteins employed in carrying out the present invention include proteins homologous to, and having essentially the same biological properties as, the nematode-inducible pore protein Tobacco RB7 disclosed herein as SEQ ID NO:2 (the same as SEQ ID NO:7). This definition is intended to encompass natural allelic variations in the pore protein. Cloned genes employed in carrying out the present invention may code for a nematode-inducible pore protein of any species of origin, including tobacco, soybean, potato, peanuts, pineapple, cotton, and vegetable crops, but preferably encode a nematode-inducible transmembrane pore protein of dicot origin. Thus, DNA sequences which hybridize to DNA of SEQ ID NO:l or SEQ ID NO:6 and code on expression for a nematode-inducible transmembrane pore protein may also be employed in carrying out the present invention. Conditions which will permit other DNA sequences which code on expression for a pore protein to hybridize to a DNA having the sequence given as SEQ ID N0:1 or SEQ ID NO:6 can be determined in a routine manner. For example, hybridization of such sequences may be carried out under conditions of reduced stringency or even stringent conditions (e.g., conditions represented by a wash stringency of 0.3 M NaCl, 0.03 M sodium citrate, 0.1% SDS at 60"C or even 70'C to DNA having the sequence given as SEQ ID NO:l or SEQ ID NO:6 herein in a standard in situ hybridization assay. See J. Sambrook et al., Molecular Cloning, A Laboratory Manual (2d Ed. 1989) (Cold Spring Harbor Laboratory)). In general, such sequences will be at least 75% homologous, 80% homologous, 85% homologous, 90% homologous, or even 95% homologous or more with the sequence given herein as SEQ ID NO:l or SEQ ID NO:6 (in the case of SEQ ID NO:6, which is a genomic sequence, such homology is with respect to the exons alone, though the homology may be considered with respect to both introns and exons) . Determinations of homology are made with the two sequences aligned for maximum matching. Gaps in either of the two sequences being matched are allowed in maximizing matching. Gap lengths of 10 or less are preferred, gap lengths of 5 or less are more preferred, and gap lengths of 2 or less still more preferred. Antisense DNAs in the present invention are used to produce the corresponding antisense RNAs. An antisense RNA is an RNA which is produced with the nucleotide bases in the reverse or opposite order for expression. Such antisense RNAs are well known. See, e.g., U.S. Patent No. 4,801,540 to Calgene Inc. In general, the antisense RNA will be at least 15 nucleotides in length, and more typically at least 50 nucleotides in length. The antisense RNA may include an intron-exon junction (i.e., one, two, or three nucleotides on either or both sides of the intron- exon junction) . Antisense RNAs which include an intron- exon junction are constructed with reference to a genomic DNA sequence. Sense DNAs employed in carrying out the present invention are of a length sufficient to, when expressed in a plant cell, supress the native expression of a nematode- inducible transmembrane pore protein as described herein in that plant cell. Such sense DNAs may be essentially an entire genomic or complementary DNA encoding the nematode- inducible transmembrane pore protein or a fragment thereof, with such fragments typically being at least 15 nucleotides in length. In an alternate embodiment of the present invention, the sense or antisense DNA in the construct is replaced with a DNA encoding an enzymatic RNA molecule (i.e., a l, ribozyme") , which enzymatic RNA molecule is directed against (i.e., cleaves) the mRNA transcript of a DNA encoding a nematode-inducible transmembrane pore protein as described hereinabove. DNA encoding enzymatic RNA molecules may be produced in accordance with known techniques. See. e.g., T. Cech et al., U.S. Patent No. 4,987,071 (the disclosure of which is to be incorporated herein by reference) . Production of such an enzymatic RNA molecule and disruption of pore protein production combats the infection of plants by nematodes in essentially the same manner as production of an antisense RNA molecule: that is, by disrupting translation of mRNA in the cell which produces the pore protein. Promoters employed in carrying out the present invention may be constitutively active promoters. Numerous constitutively active promoters which are operable in plants are available. A prefered example is the Cauliflower Mosaic Virus (CaMV) 35S promoter. In the alternative, the promoter may be a root-specific promoter or a nematode-responsive element, as explained in greater detail below. Promoters which are selectively active in plant root tissue cells employed in carrying out the present invention include DNAs homologous to, and having essentially the same biological properties as, the Tobacco RB7 root-specific gene promoter disclosed herein as SEQ ID NO:4. This definition is intended to encompass natural allelic variations therein. Such elements may be of any species of origin, including tobacco, soybean, potato, peanuts, pineapple, cotton, and vegetable crops, but preferably are of dicot origin. Thus, DNA sequences which hybridize to DNA of SEQ ID NO:4 and contain a root-specific gene promoter may also be employed in carrying out the present invention. Conditions which will permit other DNA sequences which code for a such an element to hybridize to a DNA having the sequence given as SEQ ID NO:4 can be determined in a routine manner. For example, hybridization of such sequences may be carried out under conditions as given above in connection with nematode-inducible transmembrane pore proteins. Such sequences will generally be at least 75% homologous, 80% homologous, 85% homologous, 90% homologous, or even 95% homologous or more with the sequence given herein as SEQ ID NO:4. Gaps may be introduced to maximize homology when determining homology, as discussed above. In addition, homology may be determined with respect to a 10 to 15 or even 25 or 50 base segment of a DNA having the sequence of SEQ ID NO:5 and capable of directing nematode-responsive transcription of a downstream DNA sequence (i.e., a structural gene or an antisense DNA) in a plant cell. By "base segment" is meant a continuous portion thereof which is of the indicated number of nucleotides in length. Nematode-responsive elements employed in carrying out the present invention include DNAs homologous to, and having essentially the same biological properties as, the Tobacco RB7 nematode-responsive element disclosed herein as SEQ ID NO:5. This definition is intended to encompass natural allelic variations therein. Such elements may again be of any species of origin, including tobacco, soybean, potato, peanuts, pineapple, cotton, and vegetable crops, but preferably are of dicot origin. Thus, DNA sequences which hybridize to DNA of SEQ ID NO:5 and contain a nematode-responsive element may also be employed in carrying out the present invention. Conditions which will permit other DNA sequences which code for a such an element to hybridize to a DNA having the sequence given as SEQ ID NO:5 can again be determined in a routine manner. For example, hybridization of such sequences may be carried out under conditions as given above in connection with nematode-inducible transmembrane pore proteins. Such sequences will generally be at least 75% homologous, 80% homologous, 85% homologous, 90% homologous, or even 95% homologous or more with the sequence given herein as SEQ ID NO:5. Gaps may be introduced to maximize homology when determining homology, as discussed above. In addition, homology may be determined with respect to a 10 to 15 or even 25 or 50 base segment of a DNA having the sequence of SEQ ID NO:5 and capable of directing nematode-responsive transcription of a downstream DNA sequence (i.e., a structural gene or an antisense DNA) in a plant cell. DNA constructs, or "transcription cassettes," of the present invention include, 5 1 to 3' in the direction of transcription, a promoter as discussed above, a DNA operatively associated with the promoter, and, optionally, a termination sequence including stop signal for RNA polymerase and a polyadenylation signal for polyadenylase. All of these regulatory regions should be capable of operating in the cells of the tissue to be transformed. Any suitable termination signal may be employed in carrying out the present invention, examples thereof including, but not limited to, the nos terminator, the CaMV terminator, or native termination signals derived from the same gene as the transcriptional initiation region or derived from a different gene. The term "operatively associated," as used herein, refers to DNA sequences on a single DNA molecule which are associated so that the function of one is affected by the other. Thus, a promoter is operatively associated with a DNA when it is capable of affecting the transcription of that DNA (i.e., the DNA is under the transcriptional control of the promoter) . The promoter is said to be "upstream" from the DNA, which is in turn said to be "downstream" from the promoter. The transcription cassette may be provided in a DNA construct which also has at least one replication system. For convenience, it is common to have a replication system functional in Escherichia coli , such as ColEl, pSClOl, pACYC184, or the like. In this manner, at each stage after each manipulation, the resulting construct may be cloned, sequenced, and the correctness of the manipulation determined. In addition, or in place of the E. coli replication system, a broad host range replication system may be employed, such as the replication systems of the P-l incompatibility plasmids, e.g., pRK290. In addition to the replication system, there will frequently be at least one marker present, which may be useful in one or more hosts, or different markers for individual hosts. That is, one marker may be employed for selection in a prokaryotic host, while another marker may be employed for selection in a eukaryotic host, particularly the plant host. The markers may be protection against a biocide, such as antibiotics, toxins, heavy metals, or the like; provide complementation, by imparting prototrophy to an auxotrophic host: or provide a visible phenotype through the production of a novel compound in the plant. Exemplary genes which may be employed include neomycin phosphotransferase (NPTII) , hygromycin phosphotransferase (HPT) , chloramphenicol acetyltransferase (CAT) , nitrilase, and the gentamicin resistance gene. For plant host selection, non-limiting examples of suitable markers are NPTII, providing kanamycin resistance or G418 resistance, HPT, providing hygromycin resistance, and the mutated aroA gene, providing glyphosate resistance. The various fragments comprising the various constructs, transcription cassettes, markers, and the like may be introduced consecutively by restriction enzyme cleavage of an appropriate replication system, and insertion of the particular construct or fragment into the available site. After ligation and cloning the DNA construct may be isolated for further manipulation. All of these techniques are amply exemplified in the literature and find particular exemplification in J. Sambrook et al.. Molecular Cloning, A Laboratory Manual (2d Ed. 1989) (Cold Spring Harbor Laboratory) . Vectors which may be used to transform plant tissue with DNA constructs of the present invention include both Agrobacterium vectors and ballistic vectors, as well as vectors suitable for DNA-mediated transformation. Methods of making recombinant nematode-resistant plants of the invention, in general, involve providing a plant cell capable of regeneration (the plant cell typically residing in a tissue capable of regeneration) . The plant cell is then transformed with a DNA construct comprising a transcription cassette of the present invention (as described herein) and a recombinant nematode- resistant plant regenerated from the transformed plant cell. As explained below, the transforming step is carried out by bombarding the plant cell with microparticles carrying the transcription cassette, by infecting the cell with an Agrobacterium tumefaciens containing a Ti plasmid carrying the transcription cassette, or any other technique suitable for the production of a transgenic plant. Numerous Agrobacterium vector systems useful in carrying out the present invention are known. For example, U.S. Patent No. 4,459,355 discloses a method for transforming susceptible plants, including dicots, with an Agrobacterium strain containing the Ti plasmid. The transformation of woody plants with an Agrobacterium vector is disclosed in U.S. Patent No. 4,795,855. Further, U.S. Patent No. 4,940,838 to Schilperoort et al. discloses a binary Agrobacterium vector (i.e., one in which the Agrobacterium contains one plasmid having the vir region of a Ti plasmid but no T region, and a second plasmid having a T region but no vir region) useful in carrying out the present invention. Microparticles carrying a DNA construct of the present invention, which microparticle is suitable for the ballistic transformation of a plant cell, are also useful for making transformed plants of the present invention. The microparticle is propelled into a plant cell to produce a transformed plant cell, and a plant is regenerated from the transformed plant cell. Any suitable ballistic cell transformation methodology and apparatus can be used in practicing the present invention. Exemplary apparatus and procedures are disclosed in Sanford and Wolf, U.S. Patent No. 4,945,050, and in Christou et al., U.S. Patent No. 5,015,580. When using ballistic transformation procedures, the transcription cassette may be incorporated into a plasmid capable of replicating in or integrating into the cell to be transformed. Examples of microparticles suitable for use in such systems include 1 to 5 μm gold spheres. The DNA construct may be deposited on the microparticle by any suitable technique, such as by precipitation. Plant species may be transformed with the DNA construct of the present invention by the DNA- ediated transformation of plant cell protoplasts and subsequent regeneration of the plant from the transformed protoplasts in accordance with procedures well known in the art. Any plant tissue capable of subsequent clonal propagation, whether by organogenesis or embryogenesis, may be transformed with a vector of the present invention. The term "organogenesis," as used herein, means a process by which shoots and roots are developed sequentially from meristematic centers; the term "embryogenesis," as used herein, means a process by which shoots and roots develop together in a concerted fashion (not sequentially) , whether from somatic cells or gametes. The particular tissue chosen will vary depending on the clonal propagation systems available for, and best suited to, the particular species being transformed. Exemplary tissue targets include leaf disks, pollen, embryos, cotyledons, hypocotyls, megagametophytes, callus tissue, existing meristematic tissue (e.g., apical meristems, axillary buds, and root meristems) , and induced meristem tissue (e.g. , cotyledon "meristem and hypocotyl meristem) . Plants of the present invention may take a variety of forms. The plants may be chimeras of transformed cells and non-transformed cells; the plants may be clonal transformants (e.g., all cells transformed to contain the transcription cassette) ; the plants may comprise grafts of transformed and untransformed tissues (e.g., a transformed root stock grafted to an untransformed scion in citrus species) . The transformed plants may be propagated by a variety of means, such as by clonal propagation or classical breeding techniques. For example, first generation (or Tl) transformed plants may be selfed to give homozygous second generation (or T2) transformed plants, and the T2 plants further propagated through classical breeding techniques. A dominant selectable marker (such as nptll) can be associated with the transcription cassette to assist in breeding. Some plants-parasitic nematodes from which plants may be protected by the present invention, and the corresponding plants which may be employed in practicing the present invention, are as follows: Alfalfa: Ditylenchus dipsaci, Meloidogyne hapla, Meloidogyne incognita, Meloidogyne javanica, Pratylenchus spp. , Paratylenchus spp., and Xiphinema spp.; Banana: Radopholus similis, Helicotylenchuε multicinctus , Meloidogyne incognita, M. arenaria, M. javanica. Pratylenchus coffeae, and Rotylenchuluε reniformis ; Beans & peas: Meloidogyne spp., Heterodera spp., Belonolaimus spp., Helicotylenchus spp. , Rotylenchulus reniformis , Paratrichodorus anemones, and Trichodorus spp. ; cassava: Rotylenchulus reniformis , Meloidogyne spp. cereals: Anguina tritici (Emmer, rye, spelt wheat) , Bidera avenae (oat, wheat) , Ditylenchus dipsaci (rye, oat) , Subanguina radicicola (oat, barley, wheat, rye) , Meloidogyne naasi (barley, wheat, rye) , Pratylenchus spp. (oat, wheat, barley, rye) , Paratylenchus spp. (wheat) , Tylenchorhynchus spp. (wheat, oat) ; chickpea: Heterodera cajani, Rotylenchulus reniformis, Hoplolaimuε seinhorsti , Meloidogyne spp. , Pratylenchus spp. ; Citrus: Tylenchulus semipenetrans , Radopholus similis, Radopholus citrophilus (Florida only) , Hemicycliophora arenaria, Pratylenchus spp., Meloidogyne spp., Bolonolai us longicaudatus (Florida only), Trichodorus, Paratrichodorus, Xiphinema spp. ; clover: Meloidogyne spp., Heterodera trifolii coconut: Rhadinaphelenchuε cocophiluε; coffee: Meloidogyne incognita (Most important in Brazil) , M. exigua (widespread) , Pratylenchus coffeae, Pratylenchuε brachyuruε, Radopholus similis, Rotylenchulus reniformiε, Helicotylenchuε spp. ; corn: Pratylenchuε spp. , Paratrichodoruε minor, Longidoruε spp. , Hoplolaimuε columbuε ; cotton: Meloidogyne incognita, Belonolaimus longicaudatus, Rotylenchulus reniformiε, Hoplolaimuε graleatus, Pratylenchuε spp. , Tylenchorhynchuε spp. , Paratrichodoruε minor; grapes: Xiphinema spp., Pratylenchuε vulnuε, Meloidogyne spp. , Tylenchulus εemipenetranε , Rotylenchuluε reniformiε ; grasses: Pratylenchus spp., Longidoruε spp., Paratrichodoruε chriεtiei , Xiphinema spp., Ditylenchuε spp.; peanut: Pratylenchuε spp., Meloidogyne hapla . , Meloidogyne arenaria, Criconemella spp., Belonolaimuε longicaudatuε (in Eastern United States) ; pigeonpea: Heterodera cajani, Rotylenchuluε reniformiε, Hoplolaimus seinhorεti, Meloidogyne spp. , Pratylenchuε spp. ; pineapple: Paratrichodoruε chriεtiei, Criconemella spp. , Meloidogyne spp., Rotylenchuluε reniformiε, Helicotylenchuε spp., Pratylenchuε spp., Paratylenchuε spp.; potato: Globodera roεtochienεiε , Globodera pallida, Meloidogyne spp. , Pratylenchuε spp., Trichodoruε primitivuε, Ditylenchuε spp., Paratrichodorus spp., Nacoabbus aberrans ; rice: Aphelenchiodes besseyi , Ditylenchus angustuε, Hirchmanniella spp., Heterodera oryzae, Meloidogyne spp. small fruits: Meloidogyne spp.; Pratylenchuε spp., Xiphinejπa spp., Longidoruε spp., Paratrichodorus christiei, Aphelenchoideε spp. (strawberry) ; soybean: Heterodera glycineε, Meloidogyne incognita, Meloidogyne javanica, Belonolaiiπus spp., Hoplolaimuε columbuε ; sugar beet: Heterodera εchachtii, Ditylenchuε dipεaci, Meloidogyne spp., Nacobbuε aberranε, Trichodoruε spp., Longidoruε spp., Paratrichodoruε spp. ; sugar cane: Meloidogyne spp. , Pratylenchuε spp., Radopholuε spp., Heterodera spp., Hoplolaimuε spp., Helicotylenchuε spp., Scutellonema spp., Belonolaimuε spp., Tylenchorhynchuε spp., Xiphinema spp., Longidoruε spp., Paratrichodoruε spp.; tea: Meloidogyne spp., Pratylenchuε spp., Radopholuε similis, Hemicriconemoides kanayaenεiε, Helicotylenchuε spp ' •. I Paratylenchus curvitatuε ; tobacco: Meloidogyne spp • •. I Pratylenchuε spp., Tylenchorhynchus claytoni , Globodera tabacum, Trichodoruε spp., Xiphinema americanum, Ditylenchus dipsaci (Europe only) , Paratrichodorus spp. ; tomato: Pratylenchuε spp., Meloidogyne spp.; tree fruits: Pratylenchuε spp. (apple, pear, stone fruits) , Paratylenchuε spp. (apple, pear) , Xiphinema spp. (pear, cherry, peach) , Cacopauruε peεtiε (walnut) , Meloidogyne spp. (stone fruits, apple, etc.), Longidoruε spp. (cherry), Criconemella spp. (peach) , and Tylenchuluε spp. (olive) . In view of the foregoing, it will be apparent that plants which may be employed in practicing the present invention include (but are not limited to) tobacco (Nicotiana tabacum) , potato (Solanum tuberoεum) , soybean (glycine max) , peanuts (Arachiε hypogaea) , cotton (Gossypiujπ hirεutum) , cassava (Manihot esculenta) , coffee (Cofea spp.), coconut (Cocos nucifera) , pineapple (Ananas comoεus) , citrus trees (Citrus spp.), banana (Musa spp.), corn (Zea mayε) , wheat, oats, rye, barley, rice, and vegetables such as green beans (Phaεeoluε vulgariε) , lima beans (Phaseolus limensiε) , and peas (Lathyrus spp.). Thus, an illustrative category of plants which may be used to practice the present invention are the dicots, and a more particular category of plants which may be used to practice the present invention are the members of the family Solanacae. In practice, a crop comprising a plurality of plants of the invention are planted together in an agricultural field. By "agricultural field", we mean a common plot of soil or a greenhouse, with the determinative feature typically being that a common population of nematodes infect that crop of plants. Thus, the present invention provides a method of combatting plant parasitic nematodes in an agricultural field, by planting the field with a crop of plants according to the invention. The examples which follow are set forth to illustrate the present invention, and are not to be construed as limiting thereof. EXAMPLE 1 Isolation and Expression of Genomic Root-Specific Clone RB7 Nicotiana tabacum cv Wisconsin 38 was used as the source of material for cloning and gene characterization. Genomic DNA was partially digested with Sau3A and size-fractionated on 5 to 20% potassium acetate gradients. Size fractions of 17 to 23 kb were pooled and ligated into the λ vector, EMBL3b that had been digested with BamHI and EcoRI . See A. Frischauf et al., J. Mol. Biol. 170, 827-842 (1983). A primary library of approximately 3.5 x 10 6 recombinants was screened by plaque hybridization. Positive clones were plaque purified. Restriction maps of the genomic clones were constructed using the rapid mapping procedure of Rachwitz et al.. Gene 30, 195-200 (1984). Regions encoding the root-specific clones were identified by Southern blots. To further define the transcribed regions, we took advantage of the fact that the genes are expressed at high levels. Thus, probes made of cDNA of reverse transcribed poly(A+)RNA would hybridize to Southern blots of restricted genomic clones in a manner analogous to differential screening experiments. See F. Kilcherr, Nature 321, 493-499 (1986). The clones were digested with the appropriate restriction enzymes and the fragments separated on agarose gels. These fragments were then Southern blotted to nitrocellulose filters and probed with reverse transcribed root poly(A+) NA. The probe was primed using random hexanucleotides (Pharmacia Biochemicals, Inc.) such that the 3' termini of the mRNA molecules would not be over represented among the probe. Clones hybridizing to each root-specific cDNA clone were plaque purified. Comparisons of the restriction maps of the genomic clones with genomic Southern hybridization experiments (not shown) reveal a good correlation of the sequences hybridizing to the root- specific cDNA clones. Clone λ5A hybridized to the cDNA clone TobRB7. This appears to be the genomic clone corresponding to TobRB7 and accordingly was designated as TobRB7-5A (SEQ ID NO:6) and used to generate the promoter sequences employed in the experiments described below. The cell membrane channel protein is set forth as SEQ ID NO:7. EXAMPLE 2 Identification of a Nematodβ-Responsive Element Within the TobRB7 Promoter The ability of the TobRB7 promoter region of the λ5A genomic clone to regulate the expression of a heterologous reporter gene was tested by cloning approximately 1.4 kb of 5' flanking sequence into pBI101.2 The length of the TobRB7 flanking region employed was varied to explore how various portions of the flanking region affected expression of GUS. In brief, a TobRB7 5 1 flanking region was isolated from λ5A and fused with /3-glucuronidase in the Agrobacterium binary vector, pBI 101.2. This vector contains a 3-glucuronidase (GUS) reporter gene and an nptll selectable marker flanked by the T-DNA border sequences (R. Jefferson et al. , EMBO J. 6, 3901-3907 (1987)). The TobRB7 structural gene was completely removed and the TobRB7 flanking regions fused to the GUS initiating methionene codon. The construction was mobilized into an Agrojacteriujπ host that carries a disarmed Ti-plasmid (LBA4404) capable of providing (in tranε) the vir functions required for T-DNA transfer and integration into the plant genome, essentially as described by An et al., in S. Belvin and R. Schilperoot, eds., Plant Molecular Biology Manual, Martinus Nijhoff, Dordrecht, The Netherlands, pp A3-1-19 (1988) . Nicotiana tabacum SRI leaf discs were infected and transformants selected and regenerated as described by An et al., Plant Phyεiol . 81, 301-305 (1986). Whole plants or excised root and leaf tissue were assayed for GUS expression according to Jefferson et al., supra. For histochemical staining, plants were incubated in*the 5-bromo-4-chloro-3-indolyl 3-D-glucuronide (X-GLUC) at 37 β C overnight. Tissues expressing GUS activity cleave this substrate and thereby stain blue. After the incubation the tissues were bleached in 70% ethanol. GUS enzyme activities were measured using the fluorogenic assay described by Jefferson et al. The activity of the various deletion mutants was tested. The greatest root-specific gene expression was obtained with the Δ0.6 deletion mutant (SEQ ID NO:4) . Only the Δ0.3 deletion mutant (SEQ ID NO:5) was inactive as a promoter, indicating that the TobRB7 promoter is found in the region extending about 800 nucleotides upstream from the TobRB7 structural gene. However, the Δθ.3 deletion mutant (SEQ ID NO:5) contains the RB7 nematode-responsive element, as discussed below. EXAMPLE 3 Localization of Gene Activation in Nematode infected Plants Transgenic tobacco plants prepared as described in Example 2 above were infected with tobacco root-knot nematodes (Meloidogyne incognita) in accordance with known techniques. See, e. g. , C. Opperman et al.. Plant Diεeaεe , 869-871 (October 1988) . Roots were stained for GUS activity (blue) and nematodes were stained red at three stages: (a) 24-48 hours post infection; (b) 7-10 days post infection; and (c) 20-25 days post infection. Nematodes were stained after GUS staining by incubating roots in 95% ethanol/glacial acetic acid (1:1) plus five drops of acid fushsin (per 100 mLs) for four hours, then destained in a saturated chloral hydrate solution for twelve hours to overnight. GUS activity was generally found in the elongation zone of the root. At 24-48 hours post infection, second stage juvenile nematodes have penetrated the tobacco roots, are in the corticle tissue and are migrating in search of an appropriate feeding site. Juveniles in the vascular tissue at this stage have already begun to establish feeding sites. At 7-10 days post infection, swollen late second stage juveniles are seen with their heads in the feeding site. At 20-25 days post infection, adult nematodes are seen protruding from galled root tissue, with their head still embedded in the vascular tissue and the posterior exposed to allow egg deposition. GUS activity in nematode infected root tissue of plants transformed with the various deletion mutants described in Example 2 indicated that the nematode- responsive element of the TobRB7 promoter is located in the Δ0.3 (SEQ ID NO:5) deletion mutant. Similar results are obtained with the peanut root-knot nematode (Meloidogyne arenaria) . During the foregoing experiments, it was observed that duration of gene expression in nematode- infected plants was much longer than in uninfected plants, and that the regions of gene activity were no longer restricted to the elongation zone of the root. For example, in each location where a nematode was able to establish a feeding site, gene expression continued at that site for as long as 25-30 days (i.e., the duration of the nematode life cycle) . EXAMPLE 4 Inhibition of Nematode Feeding Site Formation bv Expression of Sense or Antisense TobRB7 mRNA This example demonstrates the ability of transgenic plants expressing sense and anti-sense TobRB7 mRNA under the control of a constitutively active promoter to interfere with the establishment of root-knot nematode feeding sites. The constructions employed are described in Figure 1, and the plants were prepared in essentially the same manner as described in Example 2 above. The sense DNA employed had the sequence given herein as SEQ ID N0:1, andthe antisense DNA employed had the sequence given herein as SEQ ID NO:3. The promoter employed was the Cauliflower Mosaic Virus 35S promoter, and the termination signal employed was the noε terminator. The constructs were transferred to the Agrobacterium binary vector pBIN19 and transgenic plants were produced in essentially the same manner as described above: tobacco leaf disks were transformed and transfor ants selected on kanamycin; regenerants were allowed to self and set seeds; seeds (R2) were germinated on kanamycin and segregation of the Kan 1" marker assayed; those plants exhibiting a 3:1 segregation (i. e. , containing a single locus of integration) were allowed to self; progeny of the R2 were germinated on kanamycin to determine those R2 progeny that were homozygous for the transgene. The phenotypes of a large number of control, sense, and antisense plants were examined. Control plants looked like normal tobacco. Sense and antisense plants exhibited similar phenotypes: l)long internodes, (2) narrow and pointed leaves, and (3) early flowering. These phenotypes resemble "stress *1 phenotypes exhibited by plants grown in suboptimal conditions, such as small pots. It appears that the "stress" phenotype in sense plants results from the phenomenon of co-suppression: a phenomenon in which plants carrying transgenes in the sense orientation show reduced, rather than increased, levels of gene expression. See, e. g. , C. Napoli et al., The Plant Cell 2 , 279-289 (1990). Transgenic plants of sense transformants, anti- sense transformants, and control transformants were infected with second-stage juveniles of M. arenaria in essentially the same manner as described above. Approximately 100,000 nematodes suspended in sterile water were pipetted along the roots of plants growing on agar plates. Plants were maintained in a growth chamber at 25°C. At 24 hr post infection, juveniles were observed in various stages of root penetration on all plates. Galls were visible on all treatments by 3-5 days post infection. Roots were harvested from plates 2A, 2B, and 7 (anti-sense) ; 13 and 37 (sense) ; and 22A and 22B (control) at 21 days post-infection. Initial observations revealed substantial and extensive galling of the sense and control plants. Galls often appeared in clusters along the root. It appeared that in a number of galls, adult female nematodes had begun reproduction. In contrast, few galls were present on the anti-sense plants. Those that were present occurred singly rather than in clusters and were substantially reduced in size compared to the sense and control plants (<50% the diameter) . Two of the three plates yielded no plants with visible galling at 21 days post-infection. Roots from each treatment were stained with acid fuchsin to determine stage of nematode development and the degree of root penetration. Roots of sense and control plants were infected with numerous nematodes in various stages of development. Mature females were observed in several galls and egg production appeared to have been initiated. Galls contained numerous nematodes. Other stages observed included vermiform second-stage juveniles, swollen second-stage juveniles, and third/fourth stage juveniles. No adult males were observed within roots or on plates. Far fewer nematodes were observed in anti-sense plants. Those that were present were mostly veriform or swollen second-stage juveniles. No adult female nematodes were found. Several adult male nematodes were observed within the roots, but not on the plate surface. Galls that were present generally contained a single nematode and tended to occur at root junctions. EXAMPLE 5 Effect on Nematode Nematode Eσσ Mass Rating of Expression of Sense or Antisense TobRB7 mRNA under The Control of a Constitutive Promoter Transgenic tobacco plants expressing sense or antisense TobRB7 mRNA prepared as described above were infected with tobacco root-knot nematodes (Meloidogyne incognita) in accordance with known techniques. See, e. g. , C. Opperman et al.. Plant Diεeaεe , 869-871 (October 1988). 63 days after infection, roots were harvested, egg masses were stained with Phloxine B to facilitate counting in accordance with known techniques and egg masses counted. Both sense and antisense plants were found resistant to nematodes. These data are given in Table 1 below. TABLE 1: Egg Mass Ratings at 63 Days After Infection Transformant Egg Mass Rating Number of Eggs Plant Type Line 37 2.6+0.5 1120 sense 6 3.6+1.0 3516 antisense 20 3.8+1.3 3270 antisense 2 4.0+1.0 NA antisense 13 4.3+0.5 5400 sense 34 4.4+0.7 4594 sense 36 4.5+0.8 6980 sense 21 4.6+0.5 5300 control 22 4.7+0.5 6000 control Egg Mass Rating: 0=no egg masses; 1=<10 egg masses; 2=10-50 egg masses; 3=50-150 egg masses; 4=150-300 egg masses; 5=>300 egg masses. NA=not available. EXAMPLE 6 Inhibition of Nematode Feeding Site Formation bv Expression of Sense or Antisense TobRB7 mRNA under The Control of a Nematode-Responsive Element or a Root-Specific Gene Promoter Transgenic plants expressing sense anti-sense TobRB7 mRNA under the control of a promoter comprising a root specific gene promoter or a nematode-responsive element interfere with the establishment of root-knot nematode feeding sites. The constructions employed are described in Figure 2. Sense, antisense, and control plants were produced in essentially the same manner as described in Example 4 above, except that the root specific promoter described above and having the sequence given in SEQ ID NO:4 was employed in place of the CaMV 35S promoter. Additionally, sense, antisense, and control plants were produced in essentially the same manner as described in Example 4 above, except that the nematode-responsive element described above and having the sequence given herein as SEQ ID NO:5 was employed in place of the CaMV 35S promoter. Resistance to nematodes is shown in the same manner as described above. The foregoing examples are illustrative of the present invention, and are not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein. SEQUENCE LISTING (1) GENERAL INFORMATION: (i) APPLICANT: Conkling, Mark A. Opperman, Charles H. Acedo, Gregoria N. Song, Wen (ii) TITLE OF INVENTION: Nematode Resistant Transgenic Plants (iii) NUMBER OF SEQUENCES: 7 (iv) CORRESPONDENCE ADDRESS: (A) ADDRESSEE: Kenneth D. Sibley; Bell, Seltzer, Park and Gibson (B) STREET: Post Office Drawer 34009 (C) CITY: Charlotte (D) STATE: North Carolina (E) COUNTRY: U.S.A. (F) ZIP: 28234 (v) COMPUTER READABLE FORM: (A) MEDIUM TYPE: Floppy disk (B) COMPUTER: IBM PC compatible (C) OPERATING SYSTEM: PC-DOS/MS-DOS (D) SOFTWARE: PatentIn Release #1.0, Version #1.25 (vi) CURRENT APPLICATION DATA: (A) APPLICATION NUMBER: (B) FILING DATE: (C) CLASSIFICATION: (viii) ATTORNEY/AGENT INFORMATION: (A) NAME: Sibley, Kenneth D. (B) REGISTRATION NUMBER: 31,665 (C) REFERENCE/DOCKET NUMBER: 5051-201 (ix) TELECOMMUNICATION INFORMATION: (A) TELEPHONE: 919-881-3140 (B) TELEFAX: 919-881-3175 (C) TELEX: 575102 (2) INFORMATION FOR SEQ ID N0:1: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 938 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: cDNA ( i x) FEATURE : (A) NAME/KEY: CDS (B) LOCATION: 47..799 (ix) FEATURE: (A) NAME/KEY: mat_peptide (B) LOCATION: 47..796 (xi) SEQUENCE DESCRIPTION: SEQ ID NO:l: CTTAAATTGA GCTTCTTTTG GGGCATTTTT CTAGTGAGAA CTAAAA ATG GTG AGG 55 Met Val Arg 1 ATT GCC TTT GGT AGC ATT GGT GAC TCT TTT AGT GTT GGA TCA TTG AAG 103 He Ala Phe Gly Ser He Gly Asp Ser Phe Ser Val Gly Ser Leu Lys 5 10 15 GCC TAT GTA GCT GAG TTT ATT GCT ACT CTT CTC TTT GTG TTT GCT GGG 151 Ala Tyr Val Ala Glu Phe He Ala Thr Leu Leu Phe Val Phe Ala Gly 20 25 30 * 35 GTT GGG TCT GCT ATA GCT TAT AAT AAA TTG ACA GCA GAT GCA GCT CTT 199 Val Gly Ser Ala lie Ala Tyr Asn Lys Leu Thr Ala Asp Ala Ala Leu 40 45 50 GAT CCA GCT GGT CTA GTA GCA GTA GCT GTG GCT CAT GCA TTT GCA TTG 247 Asp Pro Ala Gly Leu Val Ala Val Ala Val Ala His Ala Phe Ala Leu 55 60 65 TTT GTT GGG GTT TCC ATA GCA GCC AAT ATT TCA GGT GGC CAT TTG AAT 295 Phe Val Gly Val Ser He Ala Ala Asn He Ser Gly Gly His Leu Asn 70 75 80 CCA GCT GTC ACT TTG GGA TTG GCT GTT GGT GGA AAC ATC ACC ATC TTG 343 Pro Ala Val Thr Leu Gly Leu Ala Val Gly Gly Asn He Thr He Leu 85 90 95 ACT GGC TTC TTC TAC TGG ATT GCC CAA TTG CTT GGC TCC ACA GTT GCT 391 Thr Gly Phe Phe Tyr Trp He Ala Gin Leu Leu Gly Ser Thr Val Ala 100 105 110 115 TGC CTC CTC CTC AAA TAC GTT ACT AAT GGA TTG GCT GTT CCA ACC CAT 439 Cys Leu Leu Leu Lys Tyr Val Thr Asn Gly Leu Ala Val Pro Thr His 120 125 130 GGA GTT GCT GCT GGG CTC AAT GGA TTA CAA GGA GTG GTG ATG GAG ATA 487 Gly Val Ala Ala Gly Leu Asn Gly Leu Gin Gly Val Val Met Glu He 135 140 145 ATC ATA ACC Tπ GCA CTG GTC TAC ACT GTT TAT GCA ACA GCA GCA GAC 535 He He Thr Phe Ala Leu Val Tyr Thr Val Tyr Ala Thr Ala Ala Asp 150 155 160 CCT AAA AAG GGC TCA CTT GGA ACC ATT GCA CCC ATT GCA ATT GGG TTC 583 Pro Lys Lys Gly Ser Leu Gly Thr He Ala Pro He Ala He Gly Phe 165 170 175 ATT GTT GGG GCC AAC ATT TTG GCA GCT GGT CCA TTC AGT GGT GGG TCA 631 He Val Gly Ala Asn He Leu Ala Ala Gly Pro Phe Ser Gly Gly Ser 180 185 190 195 ATG AAC CCA GCT CGA TCA TTT GGG CCA GCT GTG GTT GCA GGA GAC TTT 679 Met Asn Pro Ala Arg Ser Phe Gly Pro Ala Val Val Ala Gly Asp Phe 200 205 210 TCT CAA AAC TGG ATC TAT TGG GCC GGC CCA CTC ATT GGT GGA GGA TTA 727 Ser Gin Asn Trp He Tyr Trp Ala Gly Pro Leu He Gly Gly Gly Leu 215 220 225 GCT GGG TTT ATT TAT GGA GAT GTC TTT ATT GGA TGC CAC ACC CCA CTT 775 Ala Gly Phe He Tyr Gly Asp Val Phe He Gly Cys His Thr Pro Leu 230 235 240 CCA ACC TCA GAA GAC TAT GCT TAAAACTTAA AAGAAGACAA GTCTGTCTTC 826 Pro Thr Ser Glu Asp Tyr Ala 245 250 AATGTTTCTT TGTGTGTTTT CAAATGCAAT GTTGATTTTT AATTTAAGCT TTGTATATTA 886 TGCTATGCAA CAAGTTTGTT TCCAATGAAA TATCATGTTT TGGTTTCTTT TG 938 (2) INFORMATION FOR SEQ ID NO:2: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 250 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2: Met Val Arg He Ala Phe Gly Ser He Gly Asp Ser Phe Ser Val Gly 1 5 10 15 Ser Leu Lys Ala Tyr Val Ala Glu Phe He Ala Thr Leu Leu Phe Val 20 25 30 Phe Ala Gly Val Gly Ser Ala He Ala Tyr Asn Lys Leu Thr Ala Asp 35 40 45 Ala Ala Leu Asp Pro Ala Gly Leu Val Ala Val Ala Val Ala His Ala 50 55 60 Phe Ala Leu Phe Val Gly Val Ser He Ala Ala Asn He Ser Gly Gly 65 70 75 80 His Leu Asn Pro Ala Val Thr Leu Gly Leu Ala Val Gly Gly Asn He 85 90 95 Thr He Leu Thr Gly Phe Phe Tyr Trp He Ala Gin Leu Leu Gly Ser 100 105 110 Thr Val Ala Cys Leu Leu Leu Lys Tyr Val Thr Asn Gly Leu Ala Val 115 120 125 Pro Thr His Gly Val Ala Ala Gly Leu Asn Gly Leu Gin Gly Val Val 130 135 140 Met Glu He He He Thr Phe Ala Leu Val Tyr Thr Val Tyr Ala Thr 145 150 155 160 Ala Ala Asp Pro Lys Lys Gly Ser Leu Gly Thr He Ala Pro He Ala 165 170 175 He Gly Phe He Val Gly Ala Asn He Leu Ala Ala Gly Pro Phe Ser 180 185 190 Gly Gly Ser Met Asn Pro Ala Arg Ser Phe Gly Pro Ala Val Val Ala 195 200 205 Gly Asp Phe Ser Gin Asn Trp He Tyr Trp Ala Gly Pro Leu He Gly 210 215 220 Gly Gly Leu Ala Gly Phe He Tyr Gly Asp Val Phe He Gly Cys His 225 230 235 240 Thr Pro Leu Pro Thr Ser Glu Asp Tyr Ala 245 250 (2) INFORMATION FOR SEQ ID N0:3: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 938 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: cDNA (iv) ANTI-SENSE: YES (xi) SEQUENCE DESCRIPTION: SEQ ID N0:3: CAAAAGAAAC CAAAACATGA TATTTCATTG GAAACAAACT TGTTGCATAG CATAATATAC 60 AAAGCTTAAA TTAAAAATCA ACATTGCATT TGAAAACACA CAAAGAAACA TTGAAGACAG 120 ACTTGTCTTC TTTTAAGTTT TAAGCATAGT CTTCTGAGGT TGGAAGTGGG GTGTGGCATC 180 CAATAAAGAC ATCTCCATAA ATAAACCCAG CTAATCCTCC ACCAATGAGT GGGCCGGCCC 240 AATAGATCCA GTTTTGAGAA AAGTCTCCTG CAACCACAGC TGGCCCAAAT GATCGAGCTG 300 GGTTCATTGA CCCACCACTG AATGGACCAG CTGCCAAAAT GTTGGCCCCA ACAATGAACC 360 CAATTGCAAT GGGTGCAATG GTTCCAAGTG AGCCCTTTTT AGGGTCTGCT GCTGTTGCAT 420 AAACAGTGTA GACCAGTGCA AAGGTTATGA TTATCTCCAT CACCACTCCT TGTAATCCAT 480 TGAGCCCAGC AGCAACTCCA TGGGTTGGAA CAGCCAATCC ATTAGTAACG TATTTGAGGA 540 GGAGGCAAGC AACTGTGGAG CCAAGCAATT GGGCAATCCA GTAGAAGAAG CCAGTCAAGA 600 TGGTGATGTT TCCACCAACA GCCAATCCCA AAGTGACAGC TGGATTCAAA TGGCCACCTG 660 AAATATTGGC TGCTATGGAA ACCCCAACAA ACAATGCAAA TGCATGAGCC ACAGCTACTG 720 CTACTAGACC AGCTGGATCA AGAGCTGCAT CTGCTGTCAA TTTATTATAA GCTATAGCAG 780 ACCCAACCCC AGCAAACACA AAGAGAAGAG TAGCAATAAA CTCAGCTACA TAGGCCTTCA 840 ATGATCCAAC ACTAAAAGAG TCACCAATGC TACCAAAGGC AATCCTCACC ATTTTTAGTT 900 CTCACTAGAA AAATGCCCCA AAAGAAGCTC AATTTAAG 938 (2) INFORMATION FOR SEQ ID N0:4: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 706 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID N0:4: GTCCTACACA ATGTGAATTT GAATTAGTTT GGTCATACGG TATATCATAT GATTATAAAT 60 AAAAAAAATT AGCAAAAGAA TATAATTTAT TAAATATTTT ACACCATACC AAACACAACC 120 GCATTATATA TAATCTTAAT TATCATTATC ACCAGCATCA ACATTATAAT GATTCCCCTA 180 TGCGTTGGAA CGTCATTATA GTTATTCTAA ACAAGAAAGA AATπGTTCT TGACATCAGA 240 CATCTAGTAT TATAACTCTA GTGGAGCTTA CCTTTTCTTT TCCTTCTTTT TTTTCTTCTT 300 AAAAAAATTA TCACTTTTTA AATCTTGTAT ATTAGTTAAG CTTATCTAAA CAAAGTTTTA 360 AATTCATTTC TTAAACGTCC ATTACAATGT AATATAACTT AGTCGTCTCA ATTAAACCAT 420 TAATGTGAAA TATAAATCAA AAAAAGCCAA AGGGCGGTGG GACGGCGCCA ATCATTTGTC 480 CTAGTCCACT CAAATAAGGC CCATGGTCGG CAAAACCAAA CACAAAATGT GTTATTTTTA 540 ATTTTTTCCT CTTTTATTGT TAAAGTTGCA AAATGTGTTA TTTTTGGTAA GACCCTATGG 600 ATATATAAAG ACAGGTTATG TGAAACTTGG AAAACCATCA AGTTTTAAGC AAAACCCTCT 660 TAAGAACTTA AATTGAGCTT CTTTTGGGGC ATTTTTCTAG TGAGAA 706 (2) INFORMATION FOR SEQ ID NO:5: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 368 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID N0:5: AGCTTATCTA AACAAAGTTT TAAATTCATT TCTTAAACGT CCATTACAAT GTAATATAAC 60 TTAGTCGTCT CAATTAAACC ATTAATGTGA AATATAAATC AAAAAAAGCC AAAGGGCGGT 120 GGGACGGCGC CAATCATTTG TCCTAGTCCA CTCAAATAAG GCCCATGGTC GGCAAAACCA 180 AACACAAAAT GTGTTATTTT TAATTTTTTC CTCTTTTATT GTTAAAGTTG CAAAATGTGT 240 TATTTTTGGT AAGACCCTAT GGATATATAA AGACAGGTTA TGTGAAACTT GGAAAACCAT 300 CAAGTTTTAA GCAAAACCCT CTTAAGAACT TAAATTGAGC TTCTTTTGGG GCATπTTCT 360 AGTGAGAA 368 (2) INFORMATION FOR SEQ ID NO:6: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 3426 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: DNA (genomic) (ix) FEATURE: (A) NAME/KEY: promoter (B) LOCATION: 1..1877 (ix) FEATURE: (A) NAME/KEY: exon (B) LOCATION: 1954..2079 (ix) FEATURE: (A) NAME/KEY: intron (B) LOCATION: 2080..2375 " (ix) FEATURE: (A) NAME/KEY: exon (B) LOCATION: 2376..2627 (ix) FEATURE: (A) NAME/KEY: intron (B) LOCATION: 2628..2912 (ix) FEATURE: (A) NAME/KEY: exon (B) LOCATION: 2913..3284 (ix) FEATURE: (A) NAME/KEY: 5'UTR (B) LOCATION: 1878..1953 (ix) FEATURE: (A) NAME/KEY: CDS (B) LOCATION: join(1954..2079, 2376..2627, 2913..3284) (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6: GGATCCCCCT CTTTTATAAT AGAGGGTCAT TACTTTATTT ACAATAAAAT AATAAAATAA 60 AGCATATAGT GGAGGACCCA TGATGACTTG TTTCTTCCTC GATTTTCGCC GAGATTCTCT 120 CCCATAGTGC GGTTGCAACG GCCCTTGTCT GCGAGCTCGA TACTGGTTCG AGCTCGGCAT 180 TGGACCGAGC CCTCGACCTT GGTCCGAGCT CGATTCTGAC TTGGGGTCTC GGTATTCGGG 240 GTGAGTGTTG GTCGGTCTAT GCATCTTCGA TAATCTCCGT TTTGCCTCGT AGTTCGATTT 300 GGATATGAGC TCGATAATGA TACCGAGCTT GTCATTGATC GGTCTTAGAG CTCGAAGTTC 360 GACGCCTTTA CTTCGGACCT TGACCGAGCT TGTTATGTAG ATATCCTTTG ATCGAAACAT 420 TATCGTTTTG ACCAATCCGT ACGACTGACT CAAATCGATT TGACCGCACA CAAGATTATT 480 TTCGAAAGAC CCTCGACGTC TTGGAGTATA AAATAATTTA GTAAAGAGAG TAATTGTTCG 540 TTAAAAATCT TGACACCATT CCAAGCATAC CCCTTATTGT ACTTCAATTA ATTATCATTA 600 TATCAGCATA AACATTATAA TAAGTTTCTT GCGTGTTGGA ACGTCAπTT AGTTATTCTA 660 AAGAGGAAAT AGTπCTTTT TTGCTCATGA CATCAGACAT CTGGACTACT ATACTGGAGT 720 TTACCππC TTCTCCTCπ TπcπATTG TTCCTCTAAA AAAAATTATC ACTTTTTAAA 780 TGCATTAGTT AAACTTATCT CAACAACGTT TAAAATTCAT TTCTTGAATG CCCATTACAA 840 TGTAATAGTA TAACTTAATT AGTCGTCTCC ATGAACCATT AATACGTACG GAGTAATATA 900 AAACACCATT GGGGAGTTCA ATTTGCAATA ATTTCTTGCA AAAATGTAAA GTACCTTTTT 960 GTTCTTGCAA AATTTTACAA ATAAAAATTT GCAGCTCTTT TTTTTCTCTC TCTCCAAATA 1020 CTAGCTCAAA ACCCACAAAT ATTTTTGAAT TTATGGCATA CTTTTAGAAT GCGTTTGATG 1080 CAACTATTTT CCTTTAGGAA ATATTCACAA CAATCTAAGA CAATCAAAAA GTAGAAAATA . 1140 GTTTGTAAAA AGGGATGTGG AGGACATCTT AATCAAATAT TTTCAGTTTA AAACTTGAAA 1200 ATGAAAAAAC ACCCGAAAGG AAATGATTCG TTCTTTAATA TGTCCTACAC AATGTGAATT 1260 TGAATTAGTT TGGTCATACG GTATATCATA TGATTATAAA TAAAAAAAAT TAGCAAAAGA 1320 ATATAATπA TTAAATATTT TACACCATAC CAAACACAAC CGCATTATAT ATAATCπAA 1380 TTATCATTAT CACCAGCATC AACATTATAA TGATTCCCCT ATGCGTTGGA ACGTCATTAT 1440 AGTTATTCTA AACAAGAAAG AAATTTGTTC TTGACATCAG ACATCTAGTA TTATAACTCT 1500 AGTGGAGCTT ACCTTTTCTT TTCCTTCTTT TTTTTCTTCT TAAAAAAATT ATCACTTTTT 1560 AAATCTTGTA TATTAGTTAA GCTTATCTAA ACAAAGTTTT AAATTCATTT CTTAAACGTC 1620 CATTACAATG TAATATAACT TAGTCGTCTC AATTAAACCA TTAATGTGAA ATATAAATCA 1680 AAAAAAGCCA AAGGGCGGTG GGACGGCGCC AATCATπGT CCTAGTCCAC TCAAATAAGG 1740 CCCATGGTCG GCAAAACCAA ACACAAAATG TGTTATTTTT AATTTTTTCC TCTTTTATTG 1800 TTAAAGTTGC AAAATGTGTT ATTTTTGGTA AGACCCTATG GATATATAAA GACAGGTTAT 1860 GTGAAACTTG GAAAACCATC AAGTTTTAAG CAAAACCCTC TTAAGAACTT AAATTGAGCT 1920 TCTTTTGGGG CATTπTCTA GTGAGAACTA AAA ATG GTG AGG ATT GCC TTT GGT 1974 Met Val Arg He Ala Phe Gly 1 5 AGC ATT GGT GAC TCT TTT AGT GTT GGA TCA TTG AAG GCC TAT GTA GCT 2022 Ser He Gly Asp Ser Phe Ser Val Gly Ser Leu Lys Ala Tyr Val Ala 10 15 20 GAG TTT ATT GCT ACT CTT CTC TTT GTG TTT GCT GGG GTT GGG TCT GCT 2070 Glu Phe He Ala Thr Leu Leu Phe Val Phe Ala Gly Val Gly Ser Ala 25 30 35 ATA GCT TAT AGTAAGTAAC ACTTCTCTAA TTAAACTTGC ATGCTAACAT 2119 He Ala Tyr 40 AAATACTTAA TCTGCTCTAG CACTAAATAG TAAAAAGAGC AATCAGGTGC ACTAAGGTCC 2179 CATTAATTCG TTATGCACAT GCCACGGAGT CTAGAGAAAG ACTAGACTGG CTCTATCATA 2239 TTCAATTTTA CCTTACATTT TACTAGATGC CGTTTTCTCA ATCCATAACC GAAAACAACA 2299 TAACTTTTAC AGTTACACCA AGACTGCCTA ATTAACCTTT TTTTTTTTTT TTTTTGCTTT 2359 GTGGGGTGAT TTTGTA GAT AAA TTG ACA GCA GAT GCA GCT CTT GAT CCA 2408 Asp Lys Leu Thr Ala Asp Ala Ala Leu Asp Pro 45 50 GCT GGT CTA GTA GCA GTA GCT GTG GCT CAT GCA TTT GCA TTG TTT GTT 2456 Ala Gly Leu Val Ala Val Ala Val Ala His Ala Phe Ala Leu Phe Val 55 60 65 GGG GTT TCC ATA GCA GCC AAT ATT TCA GGT GGC CAT TTG AAT CCA GCT 2504 Gly Val Ser He Ala Ala Asn He Ser Gly Gly His Leu Asn Pro Ala 70 75 80 85 GTA ACT πG GGA TTG GCT GTT GGT GGA AAC ATC ACC ATC TTG ACT GGC 2552 Val Thr Leu Gly Leu Ala Val Gly Gly Asn He Thr He Leu Thr Gly 90 95 100 TTC TTC TAC TGG ATT GCC CAA TTG CTT GGC TCC ACA GTT GCT TGC CTC 2600 Phe Phe Tyr Trp He Ala Gin Leu Leu Gly Ser Thr Val Ala Cys Leu 105 110 115 CTC CTC AAA TAC GTT ACT AAT GGA TTG GTATGTACTG CTATCATTTT 2647 Leu Leu Lys Tyr Val Thr Asn Gly Leu 120 125 CAATCCATAT TATATGTCTT πTATATTπ TCACAACTTC AATAAAAAAA CAACTTTACC 2707 TAAGACCAGC CTAAGCCGTC GTATAGCCGT CCATCCAACC CTTTAAATTA AAAAGAGCCG 2767 GCATAGTCAT AATATATGTA TATTTCATGT AGAATATTTG TATAATTAGT GTATATTGTA 2827 CGTATATCGA CTAGAAAAAA ATAAATAATG AATATGACTG TTTATTTGTA ATTGGAGTTG 2887 GGCCTCATAT GTTGGTTTTT GGCAG GCT GTT CCA ACC CAT GGA GTT GCT GCT 2939 Ala Val Pro Thr His Gly Val Ala Ala 130 135 GGG CTC AAT GGA TTA CAA GGA GTG GTG ATG GAG ATA ATC ATA ACC TTT 2987 Gly Leu Asn Gly Leu Gin Gly Val Val Met Glu He He He Thr Phe 140 145 150 GCA CTG GTC TAC ACT GTT TAT GCA ACA GCA GCA GAC CCT AAA AAG GGC 3035 Ala Leu Val Tyr Thr Val Tyr Ala Thr Ala Ala Asp Pro Lys Lys Gly 155 160 165 TCA CTT GGA ACC ATT GCA CCC ATT GCA ATT GGG TTC ATT GTT GGG GCC 3083 Ser Leu Gly Thr He Ala Pro He Ala He Gly Phe He Val Gly Ala 170 175 180 AAC ATT TTG GCA GCT GGT CCA TTC AGT GGT GGG TCA ATG AAC CCA GCT 3131 Asn He Leu Ala Ala Gly Pro Phe Ser Gly Gly Ser Met Asn Pro Ala 185 190 195 CGA TCA TTT GGG CCA GCT GTG GTT GCA GGA GAC TTT TCT CAA AAC TGG 3179 Arg Ser Phe Gly Pro Ala Val Val Ala Gly Asp Phe Ser Gin Asn Trp 200 205 210 215 ATC TAT TGG GCC GGC CCA CTC ATT GGT GGA GGA TTA GCT GGG TTT ATT 3227 He Tyr Trp Ala Gly Pro Leu He Gly Gly Gly Leu Ala Gly Phe He 220 225 230 TAT GGA GAT GTC TTT ATT GGA TGC CAC ACC CCA CTT CCA ACC TCA GAA 3275 Tyr Gly Asp Val Phe He Gly Cys His Thr Pro Leu Pro Thr Ser Glu 235 240 245 GAC TAT GCT TAAAACTTAA AAGAAGACAA GTCTGTCTTC AATGTTTCTT 3324 Asp Tyr Ala 250 TGTGTGTTTT CAAATGCAAT GTTGATTTTT AATTTAAGCT TTGTATATTA TGCTATGCAA 3384 CAAGTTTGTT TCCAATGAAA TATCATGTTT TGGTTTCTTT TG 3426 (2) INFORMATION FOR SEQ ID NO:7: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 250 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7: Met Val Arg He Ala Phe Gly Ser He Gly Asp Ser Phe Ser Val Gly 1 5 10 15 Ser Leu Lys Ala Tyr Val Ala Glu Phe He Ala Thr Leu Leu Phe Val 20 25 30 Phe Ala Gly Val Gly Ser Ala He Ala Tyr Asp Lys Leu Thr Ala Asp 35 40 45 Ala Ala Leu Asp Pro Ala Gly Leu Val Ala Val Ala Val Ala His Ala 50 55 60 Phe Ala Leu Phe Val Gly Val Ser He Ala Ala Asn He Ser Gly Gly 65 70 75 80 His Leu Asn Pro Ala Val Thr Leu Gly Leu Ala Val Gly Gly Asn He 85 90 95 Thr He Leu Thr Gly Phe Phe Tyr Trp He Ala Gin Leu Leu Gly Ser 100 105 110 Thr Val Ala Cys Leu Leu Leu Lys Tyr Val Thr Asn Gly Leu Ala Val 115 120 125 Pro Thr His Gly Val Ala Ala Gly Leu Asn Gly Leu Gin Gly Val Val 130 135 140 Met Glu He He He Thr Phe Ala Leu Val Tyr Thr Val Tyr Ala Thr 145 150 155 160 Ala Ala Asp Pro Lys Lys Gly Ser Leu Gly Thr He Ala Pro He Ala 165 170 175 He Gly Phe He Val Gly Ala Asn He Leu Ala Ala Gly Pro Phe Ser 180 185 190 Gly Gly Ser Met Asn Pro Ala Arg Ser Phe Gly Pro Ala Val Val Ala 195 200 205 Gly Asp Phe Ser Gin Asn Trp He Tyr Trp Ala Gly Pro Leu He Gly 210 215 220 Gly Gly Leu Ala Gly Phe He Tyr Gly Asp Val Phe He Gly Cys His 225 230 235 240 Thr Pro Leu Pro Thr Ser Glu Asp Tyr Ala 245 250

Claims: THAT WHICH IS CLAIMED IS: 1. A DNA construct comprising a transcription cassette, which construct comprises, in the 5 1 to 3 1 direction, a promoter operable in a plant cell, and a DNA comprising at least 15 nucleotides of a DNA encoding a nematode-inducible transmembrane pore protein in either (a) the opposite orientation for expression or (b) the proper orientation for expression. 2. A DNA construct according to claim 1, which DNA encoding a nematode-inducible transmembrane pore protein is selected from the group consisting of: (a) isolated DNA having the sequence given herein as SEQ ID N0:1 or SEQ ID NO: 6; (b) isolated DNA which hybridizes to isolated DNA of (a) above and which encodes a nematode inducible transmembrane pore protein; and (c) isolated DNA differing from the isolated DNAs of (a) and (b) above in nucleotide sequence due to the degeneracy of the genetic code, and which encode a nematode-inducible transmembrane pore protein. 3. A DNA construct according to claim 1, which DNA comprising at least 15 nucleotides of a DNA encoding a nematode-inducible transmembrane pore protein is a sense DNA in the proper orientation for expression. 4. A DNA construct according to claim 1, which DNA comprising at least 15 nucleotides of a DNA encoding a nematode-inducible transmembrane pore protein is an antisense DNA in the opposite orientation for expression. 5. A DNA construct according to claim 4, which antisense DNA includes an intron-exon junction. 6. A DNA construct according to claim 4, which antisense DNA has the sequence given herein as SEQ ID NO:3. 7. A DNA construct according to claim 1, which promoter is constitutively active in plant cells. 8. A DNA construct according to claim 1, which promoter is selectively active in plant root tissue cells. 9. A DNA construct according to claim 1, which promoter is a Cauliflower Mosaic Virus 35S promoter. 10. A DNA construct according to claim 1, which promoter is activated by a plant-parasitic nematode. 11. A DNA construct according to claim 1, which promoter is a nematode-responsive element selected from the group consisting of: (i) isolated DNA having the sequence given herein as SEQ ID NO:5; and (ii) isolated DNA which hybridizes to isolated DNA of (i) above and which encodes a nematode responsive element. 12. A DNA construct according to claim 1, which promoter is an RB7 nematode-responsive element. 13. A DNA construct according to claim 1 carried by a plant transformation vector. 14. A DNA construct according to claim 1 carried by a plant transformation vector, which plant transformation vector is an Agrobacterium tumefacienε vector. 15. A nematode-resistant transgenic plant comprising plant cells containing a DNA construct comprising a transcription cassette, which construct comprises, in the 5' to 3 1 direction, a promoter operable in said plant cells, and a DNA comprising at least 15 nucleotides of a DNA sequence encoding a nematode- inducible transmembrane pore protein in either (a) the opposite orientation for expression or (b) the proper orientation for expression. 16. A plant according to claim 15, which plant is a dicot. 17. A plant according to claim 15, which plant is a dicot selected from the group consisting of tobacco, potato, soybean, peanuts, pineapple, and cotton. 18. A plant according to claim 15, which plant is a member of the family Solanacae. 19. A plant according to claim 15, which DNA sequence encoding a nematode-inducible transmembrane pore protein is selected from the group consisting of: (a) isolated DNA having the sequence given herein as SEQ ID N0:1 or SEQ ID NO:6; (b) isolated DNA which hybridizes to isolated DNA of (a) above and which encodes a nematode inducible transmembrane pore protein; and (c) isolated DNA differing from the isolated DNAs of (a) and (b) above in nucleotide sequence due to the degeneracy of the genetic code, and which encode a nematode-inducible transmembrane pore protein. 20. A plant according to claim 15, which DNA comprising at least 15 nucleotides of a DNA encoding a nematode-inducible transmembrane pore protein is a sense DNA in the proper orientation for expression. 21. A plant according to claim 15, which DNA comprising at least 15 nucleotides of a DNA encoding a nematode-inducible transmembrane pore protein is an antisense DNA in the opposite orientation for expression. 22. A plant according to claim 15, which promoter is constitutively active in plant cells. 23. A plant according to claim 15, which promoter is selectively active in plant root tissue cells. 24. A plant according to claim 15, which promoter is activated by a plant-parasitic nematode. 25. A plant according to claim 15, which promoter is a nematode-responsive element selected from the group consisting of: (i) isolated DNA having the sequence given herein as SEQ ID NO:5; and (ii) isolated DNA which hybridizes to isolated DNA of (i) above and which encodes a nematode responsive element. 26. A crop comprising a plurality of plants according to claim 15 planted together in an agricultural field. 27. A method of combatting a plant parasitic nematodes in an agricultural field, comprising planting the field with a crop of plants according to claim 15. 28. A method of making a recombinant pathogen- resistant plant, said method comprising: providing a plant cell capable of regeneration; transforming said plant cell with a DNA construct comprising a transcription cassette, which construct comprises, in the 5 1 to 3' direction, a promoter operable in said plant cell, and a DNA comprising at least 15 nucleotides of a DNA sequence encoding a nematode- inducible transmembrane pore protein in either (a) the opposite orientation for expression or (b) the proper orientation for expression; and then regenerating a recombinant nematode-resistant plant from said transformed plant cell. 29. A method according to claim 28, wherein said plant cell resides in a plant tissue capable of regeneration. 30. A method according to claim 28, wherein said transforming step is carried out by bombarding said plant cell with microparticles carrying said transcription cassette. 31. A method according to claim 28, wherein said transforming step is carried out by infecting said cells with an Agrobacterium tumefacienε containing a Ti plasmid carrying said transcription cassette. 32. A DNA construct comprising a transcription cassette, which construct comprises, in the 5 * to 3' direction, a promoter operable in a plant cell, and a DNA encoding an enzymatic RNA molecule directed against the mRNA transcript of a DNA sequence encoding a nematode- inducible transmembrane pore protein. 33. A DNA construct according to claim 32, which DNA sequence encoding a nematode-inducible transmembrane pore protein is selected from the group consisting of: (a) isolated DNA having the sequence given herein as SEQ ID NO:l or SEQ ID NO:6; (b) isolated DNA which hybridizes to isolated DNA of (a) above and which encodes a nematode inducible transmembrane pore protein; and (c) isolated DNA differing from the isolated DNAs of (a) and (b) above in nucleotide sequence due to the degeneracy of the genetic code, and which encode a nematode-inducible transmembrane pore protein. 34. A DNA construct according to claim 32, which promoter is constitutively active in plant cells. 35. A DNA construct according to claim 32, which promoter is selectively active in plant root tissue cells. 36. A DNA construct according to claim 32, which promoter is activated by a plant-parasitic nematode. 37. A DNA construct according to claim 32, which promoter is a nematode-responsive element selected from the group consisting of: (i) isolated DNA having the sequence given herein as SEQ ID NO:5; and (ii) isolated DNA which hybridizes to isolated DNA of (i) above and which encodes a nematode responsive element. 38. A nematode-resistant transgenic plant comprising plant cells containing a DNA construct according to claim 32. 39. A crop comprising a plurality of plants according to claim 38 planted together in an agricultural field. 40. A method of combatting a plant parasitic nematodes in an agricultural field, comprising planting the field with a crop of plants according to claim 38. 41. A method of making a recombinant pathogen- resistant plant, said method comprising: providing a plant cell capable of regeneration; transforming said plant cell with a DNA construct according to claim 32; and then regenerating a recombinant nematode-resistant plant from said transformed plant cell.

Inventors: ACEDO GREGORIA N, CONKLING MARK A, OPPERMAN CHARLES H, SONG WEN, ACEDO, GREGORIA, N., CONKLING, MARK, A., OPPERMAN, CHARLES, H., SONG, WEN
Applicants: ACEDO GREGORIA N, CONKLING MARK A, OPPERMAN CHARLES H, SONG WEN, UNIV NORTH CAROLINA, ACEDO, GREGORIA, N., CONKLING, MARK, A., NORTH CAROLINA STATE UNIVERSITY, OPPERMAN, CHARLES, H., SONG, WEN
Application year: 1994
Main classification: C12N15
IPC codes: A01H5, C07K14, C12N15